Improving motor fuels by refining them with maleic anhydride



United States Patent IMPROVING MOTOR FUELS BY REFINING THEM WITH MALEIC AN-HYDRIDE Hillis O. Folkins' and Adolph Kempfl Crystal Lake, 111., assiguors to The Pure Oil Company, Chicago, 111., a corporation of Ohio No: Drawing. Application July 16, 1953, Serial No. 368,517

2 Claims. (Cl. 1'96--39) This invention is directed to improving the characteristics of catalytically cracked gasoline. It more specifically relates to a method for improving the octanenumher and lead susceptibility of motor fuels produced in catalytic cracking-processes.

To keep apace with the ever changing fuel requirementsof reciprocating internal combustion engines using spark-ignited, petroleum derived fuels, a heavy burden has been placed on the ingenuity of refiners of petroleum products. The design. and development of higher com,- pression and greater horsepower engines by the automotive industry has emphasized the need for premium fuels having a sufficient octane rating which will meet engine requirements. Fortunately, through the use 'of catalytic cracking, the petroleum industry has made available high quality .fuels for use in these new engines. In the productionof these fuels by catalytic cracking, the operating conditions employed have an effect on. the characteristics of the gasoline produced andpermit variations in quality to be obtained. However economic consideration of market requirements and operating costs generally dictate optimum operating, conditions that can be' used. -I-t therefore becomes necessary in some instances to augmentthe catalytic cracking process with complementary treating processes toenhance further certain characteristics of catalytic cracked gasolines.

It is therefiore an object. of this invention fo provide a method for finishing acatalytically cracked gasoline. It is a further object to treat gasolines produced by catalytic cracking processes with a chemical reagent to increase the octane number andlead susceptibility of the gasoline. Another objectis to improve the engine cleanliness characteristics of the gasoline. These and other objects will become more apparent from the following discussion of the instant invention.

Catalytic cracking processes employing either fixed or moving beds of catalysts are given operating flexibility by means of such variables as feed stock, operating conditions and catalysts. Generally these conditions are varied to produce optimum improvement rather than maximum improvement because of the economic considerations mentioned above. However even operating under severe conditions to produce optimum quality produces an inimical effect which is reflected in the difliculty experienced in finishing catalytically cracked gasolines to improve further their octane number and lead susceptibility. While most variables have little or no effect on these quality characteristics, operating conditions such as percentage conversion, reactor temperature and recycle ratio can be varied to influence these qualities. Recycle operation is employed to increase the ultimate yield of gasoline from a limited feed stock supply where adequate capacity is available in the catalytic cracking unit. Operating under these conditions produces a gasoline which is less tractable to further enhancement in the octane number and lead susceptibility by means of complementary refining processes. According to this invention it has been found that octane ratings and lead susceptibility of gasolines produced in catalytic cracking units operating under more severe conditions than normal can be increased materially by selectively treating the lower boiling, range fractions of thegasoline with small amounts of unsaturated dibasic acids or their anhydrides. Examples of these are maleic anhydride and male'ic acid. Other acids or anhydrides which may be used include fumaric, citraconi'c, mesaconic, itaconic, etc.

The manipulative operation of this invention involves the utilization of split treat techniques, an expedient which has long been employed in the refining of petroleum products. In reviewing the prior art, it is seen that the applications of this technique, which involves the separation of a petroleum distillate into several fractions and the separate. treatment of each fraction, are varied. As opposed to. treating of an unfractionated' distillate, use of a split treat process permits greater economies to be effected in the use of the reagents along. with additional improvements in product properties. For example, in the desulfurization of cracked gasolines. the distillate is separated into light and. heavy fractions. The light fraction treated with a mild reagent, whereas the heavy fraction is treated with a stronger reagent such as sulfuric acid. This method precludes the loss of the volatile constituents that wouldoccur 'sulfu'ric acid" were used to treat the total distillate. Al'so, iii-other instances,v the sulfor distribution effected by fractionation permits varying amounts of reagent to be employed for each. fraction treated} resulting lIL'B. reduction in the total amounts of treating reagent used! in the process. In. the refining of kerosene thisrmethod is also employed. In conventional fsplit treat processes described in the prior art, the final product is preparedhy reblend'ihg, the several fractions which have been separately treated. As distinguished from the prior art however, the instant invention only treats one of the fractions to accomplish the objectives of thisdnvention. To demonstrate the eifectiveness. of this invention a .IOI)4-'0'O' boiling range. gasoline was producedinv a fluid catalytic cracking process operating with a recycle ratio of l-PA to l\, a reactor temperature of about 925 F;',. using a natural acid clay catalyst and at a conversion of"f5f5"%. This gasoline was fractionated into cuts. having a 51) F. boiling range... The individual cuts. werev treated with maleic anhydride at room temperature employing an amount of maleic anhydriide equal to. about. 10% by weight of. the 'gasolinefraction treated. The three fractions boiling below about 300 F. showed an increase in octane characteristics, especially lead susceptibility, following this treatment. The results of these tests are shown in Table I.

TABLE I F. C. C. gasoline-maleic anhydride treated OCTANE RATINGS 1 -190 F. -240 F. 240-290 F.

Cut Orig. Treated Orig. #1 #2 Orig. Treated Clear. 75. 2 77. 8 75. 0 78. 3 I '"fs' 3.0 81.2 85.4 81.8

1 Motor test procedure for determining knock characteristics of motor fuels (ORG Designation F-2-545), described in CRO Handbook, 1946, Coordinating Research Council, January 1946.

However when the 290340 F. cut was similarly treated, a leaded octane value of 82.5 was obtained as compared to an octane rating of 84.1 on the untreated 290340' F. fraction. On the other hand, when the full boiling range (100-400 F.) gasoline was treated with maleic anhydried, this treatment showed no effect on the octane ratings. Each of the fractions which were contacted with maleic anhydride were caustic treated and water washed, prior to obtaining the octane rating, in order to remove any traces of maleic anhydride from the treatedgasoline. However other purification solutions or techniques, such as other alkaline solutions, adsorption, solvent extraction, and others, may be employed to efiect this objective. In addition to the removal of excess treating agent or reaction product from the gasoline fraction by the methods outlined above, it may be desirable, in some cases, to distill the treated fraction before reblending it with the untreated fraction of gasoline. It is thus seen that fractions boiling below about 300 F. of a catalytically cracked gasoline produced under severe operating conditions can be treated with maleic anhydride to improve the octane ratings and lead susceptibility of these fractions. The fractions thus treated may be reblended with the higher boiling fractions of the gasoline giving a full range gasoline having octane characteristics superior to those possessed by the original gasoline produced by catalytic cracking processes.

The foregoing is intended to be an illustrative and nonlirniting example of the instant invention. In practicing this invention, the portions into which the 100300 F. boiling range fraction may be split may vary widely without detracting from the advantages of this invention. The amount of maleic anhydride or other treating agent which is employed will, of course, depend upon the nature of the catalytically cracked gasoline being treated. In general about 0.1% to by weight of gasoline fraction being treated may be used, although in some instances as little as 0.05% by weight may be effective. On the other hand, quantities as high as byweight or higher may be desirable in exceptional cases. This treatment may be carried out in any conventional apparatus and preferably is done with the gasoline in the liquid phase, although in certain instances vapor phase or vapor-liquid phase treatment may be desirable using appropriate temperatures and pressures to bring about these conditions. Similarly, the maleic anhydride or other refining agent may be employed in either the liquid, solid or vapor state. 7

Catalytically cracked gasolines which may be most successfully treated by'means of the instant invention are those which are produced in catalytic cracking processes at conversions of around 55% or above. Operating conditions wherein this degree of severity will be attained are dependent upon the charge stock and upon the activity and type of the cracking catalyst. For fluid cracking processes the operating conditions for such conversion are defined approximately as follows:

To facilitate further a definition of the subject inven tion, these conditions will hereinafter in the appended claims be referred to as severe conditions.

It is thus seen that by this invention the characteristics of catalytically cracked gasolines can be affected by treating selected low boiling fractions with the refining agents of this invention and reblending the low boiling treated fractions with the higher boiling untreated fractions to produce a full boiling range gasoline. Variations in the operating techniques employed in the foregoing examples will be apparent to those skilled in the art and are accordingly within the scope of the invention as defined in the instant claims.

What is claimed is:

1. A method for improving the detonation characteristics of a petroleum derived, spark-ignited internal combustion engine fuel which comprises thermally decomposing a gas oil in a fluid catalytic cracking process operated at a conversion of not less than about to produce a catalytically cracked gasoline having a boiling range of from about 100 F. to about 400 F., separating said gasoline into a low boiling range fraction having the same initial boiling point as said gasoline and an end boiling point of about 300 F. and a high boiling range fraction having an end boiling point the same as said gasoline, said fractions having continuous boiling ranges, contacting said low boiling range fraction with 01-10% by weight of maleic anhydride to enhance the detonation characteristics of said low boiling range fraction, purifying said low boiling range fraction with an aqueous caustic solution followed thereafter by water washing, and reblending the thus treated low boiling range fraction with said higher boiling fraction to produce a full boiling range gasoline.

2. A method in accordance with claim 1 in which said contacting is carried out at a temperature of about F.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A METHOD FOR IMPROVING THE DETONATION CHARACTERISTICS OF A PETROLEUM DERIVED, SPARK-IGNITED INTERNAL COMBUSTION ENGINE FUEL WHICH COMPRISES THERMALLY DECOMPOSING A GAS OIL IN FLUID CATALYTIC CRACKING PROCESS OPERATED AT A CONVERSION OF NOT LESS THAN ABOUT 55% TO PRODUCE A CATALYTICALLY CRACKED GASOLINE HAVING A BOILING RANGE FROM ABOUT 100* F. TO ABOUT 400* F., SEPARATING SAID GASOLINE INTO A LOW BOILING RANGE FRACTION HAVING THE SAME INITIAL BOILING POINT AS SAID GASOLINE AND AN END BOILING POINT OF ABOUT 300* F. AND A HIGH BOILING RANGE FRACTION HAVING AN END BOILING POINT THE SAME AS SAID GASOLINE, SAID FRACTIONS HAVING CONTINUOUS BOILING RANGES, CONTACTING SAID LOW BOILING RANGE FRACTION WITH 0.1-10% BY WEIGHT OF MALEIC ANHYDRIDE TO ENHANCE THE DETONATION CHARACTERISTICS OF SAID LOW BOILING RANGE FRACTION, PURIFYING SAID LOW BOILING RANGE FRACTION WITH AN AQUEOUS CAUSTIC SOLUTION FOLLOWED THEREAFTER BY WATER WASHING, AND REBLENDING THE THUS TREATED LOW BOILING RANGE FRACTION WITH SAID HIGHER FRACTION TO PRODUCE A FULL BOILING RANGE GASOLINE. 